1. Technical Field
The present disclosure relates to a method for making carbon nanotube film.
2. Description of Related Art
Carbon nanotubes (CNTs) are a novel carbonaceous material and have received a great deal of interest since the early 1990s. Carbon nanotubes have interesting and potentially useful electrical and mechanical properties. Due to these and other properties, carbon nanotubes have become an important new material for use in a variety of fields. However, the acquired carbon nanotubes are generally in a form of particles or powder and that is inconvenient for applications.
Currently, different methods are widely used for fabricating carbon nanotube films including a growing method, a spraying method, and a Langmuir-Blodgett (LB) method.
In the growing method, a carbon nanotube film is grown on a substrate by using a chemical vapor deposition (CVD). Multiple catalyst layers are formed on the substrate and reaction conditions of the CVD is controlled. In the spraying method, carbon nanotubes, dispersed in a solvent, are sprayed on a substrate, and the solvent is dried to form a carbon nanotube film. In the LB method, carbon nanotubes are dispersed in a solvent to form a solution, and another solution having a different density is mixed with the carbon nanotube solution, thereby causing the carbon nanotubes to float on the surface of the mixture to form a carbon nanotube film.
However, the carbon nanotube film manufactured by the growing method is not a free standing film. The thickness of the carbon nanotube film manufactured by the spraying method is not uniform. Carbon nanotubes in the carbon nanotube film acquired by the LB method are disorderly aligned.
Referring to FIG. 6, a conventional method for making the carbon nanotube film, according to the prior art, includes: (a) providing a carbon nanotube array 12; (b) pulling out a carbon nanotube film 14 from the carbon nanotube array 12 by using an adhesive tape. In step (b), the carbon nanotube array 12 is contacted by the adhesive tape, and the adhesive tape is moved at a speed along a direction substantially perpendicular to a growth orientation of carbon nanotubes, thereby drawing a carbon nanotube film 14 from the carbon nanotube array 12. The carbon nanotubes in the carbon nanotube film 14 can be distributed uniformly and aligned orderly. However, the adhesive tape is soft, a flat contacting surface between the carbon nanotube array 12 and the adhesive tape cannot be easily formed. Therefore, the carbon nanotubes cannot be firmly adhered on the contact surface, during the drawing process some of the carbon nanotubes may detach from the adhesive tape, the carbon nanotubes contacted with the adhesive tape cannot be simultaneously pulled off from the substrate. Thus, a discontinuous spot 16 can be appeared in the carbon nanotube array 12, and a nonuniform thickness or a gap can be formed in the carbon nanotube film 14. The discontinuous spot 16 can be a small inflexion which appears in a boundary between the carbon nanotube array 12 and the carbon nanotube film 14 when the carbon nanotubes adhered by the adhesive tape are not synchronously pulled away from the substrate.
What is needed, therefore, is to provide a method for making a more continuous and uniform carbon nanotube film.